This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. To evaluate the safety and tolerability of topical cidofovir in HIV-infected subjects with high-grade perianal squamous intraepithelial neoplasia (perianal HSIL). (method: self-report daily sign &symptom diary, laboratory assessments)